diff --git a/src/core/slaveinterface.cpp b/src/core/slaveinterface.cpp
index 88f649c8..6eb2b08d 100644
--- a/src/core/slaveinterface.cpp
+++ b/src/core/slaveinterface.cpp
@@ -1,441 +1,427 @@
 /* This file is part of the KDE libraries
    Copyright (C) 2000 David Faure <faure@kde.org>
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License version 2 as published by the Free Software Foundation.
 
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.
 
    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
 */
 
 #include "slaveinterface.h"
 #include "slaveinterface_p.h"
 #include "usernotificationhandler_p.h"
 
 #include "slavebase.h"
 #include "connection_p.h"
 #include "commands_p.h"
 #include "hostinfo.h"
 #include <qplatformdefs.h>
 #include <signal.h>
 #include <klocalizedstring.h>
 #include <time.h>
 
 #include <QDebug>
 
 #include <QDBusConnection>
 #include <QPointer>
 #include <QDataStream>
 #include <QSslCertificate>
 #include <QSslError>
 
 using namespace KIO;
 
 Q_GLOBAL_STATIC(UserNotificationHandler, globalUserNotificationHandler)
 
 SlaveInterface::SlaveInterface(SlaveInterfacePrivate &dd, QObject *parent)
     : QObject(parent), d_ptr(&dd)
 {
     connect(&d_ptr->speed_timer, &QTimer::timeout, this, &SlaveInterface::calcSpeed);
+    d_ptr->transfer_details.reserve(max_count);
 }
 
 SlaveInterface::~SlaveInterface()
 {
     // Note: no Debug() here (scheduler is deleted very late)
 
     delete d_ptr;
 }
 
 void SlaveInterface::setConnection(Connection *connection)
 {
     Q_D(SlaveInterface);
     d->connection = connection;
 }
 
 Connection *SlaveInterface::connection() const
 {
     const Q_D(SlaveInterface);
     return d->connection;
 }
 
 static KIO::filesize_t readFilesize_t(QDataStream &stream)
 {
     KIO::filesize_t result;
     stream >> result;
     return result;
 }
 
 bool SlaveInterface::dispatch()
 {
     Q_D(SlaveInterface);
     Q_ASSERT(d->connection);
 
     int cmd;
     QByteArray data;
 
     int ret = d->connection->read(&cmd, data);
     if (ret == -1) {
         return false;
     }
 
     return dispatch(cmd, data);
 }
 
 void SlaveInterface::calcSpeed()
 {
     Q_D(SlaveInterface);
     if (d->slave_calcs_speed || !d->connection->isConnected()) { // killing a job results in disconnection but the timer never stops
         d->speed_timer.stop();
         return;
     }
 
-    const qint64 currentTime = QDateTime::currentMSecsSinceEpoch();
-    const qint64 diff = currentTime - d->start_time;
-    if (diff - d->last_time >= 900) {
-        d->last_time = diff;
-        if (d->nums == max_nums) {
-            // let's hope gcc can optimize that well enough
-            // otherwise I'd try memcpy :)
-            for (unsigned int i = 1; i < max_nums; ++i) {
-                d->times[i - 1] = d->times[i];
-                d->sizes[i - 1] = d->sizes[i];
-            }
-            d->nums--;
-        }
-        d->times[d->nums] = diff;
-        d->sizes[d->nums++] = d->filesize - d->offset;
-
-        KIO::filesize_t lspeed = 1000 * (d->sizes[d->nums - 1] - d->sizes[0]) / (d->times[d->nums - 1] - d->times[0]);
+    // Note for future reference: A list is maintained for sizes and times.
+    // Minimum list size is 1 and maximum list size is 8. Delta is calculated
+    // using first and last item from the list.
 
-//qDebug() << (long)d->filesize << diff
-//          << long(d->sizes[d->nums-1] - d->sizes[0])
-//          << d->times[d->nums-1] - d->times[0]
-//          << long(lspeed) << double(d->filesize) / diff
-//          << convertSize(lspeed)
-//          << convertSize(long(double(d->filesize) / diff) * 1000);
+    const qint64 elapsed_time = d->elapsed_timer.elapsed();
+    if (elapsed_time >= 900) {
+        if (d->transfer_details.count() == max_count) {
+            d->transfer_details.removeFirst();
+        }
 
+        const SlaveInterfacePrivate::TransferInfo first = d->transfer_details.first();
+        const SlaveInterfacePrivate::TransferInfo last = {elapsed_time, (d->filesize - d->offset)};
+        KIO::filesize_t lspeed = 1000 * (last.size - first.size) / (last.time - first.time);
         if (!lspeed) {
-            d->nums = 1;
-            d->times[0] = diff;
-            d->sizes[0] = d->filesize - d->offset;
+            d->transfer_details.clear();
         }
+        d->transfer_details.append(last);
+
         emit speed(lspeed);
     }
 }
 
 bool SlaveInterface::dispatch(int _cmd, const QByteArray &rawdata)
 {
     Q_D(SlaveInterface);
     //qDebug() << "dispatch " << _cmd;
 
     QDataStream stream(rawdata);
 
     QString str1;
     qint32 i;
     qint8 b;
     quint32 ul;
 
     switch (_cmd) {
     case MSG_DATA:
         emit data(rawdata);
         break;
     case MSG_DATA_REQ:
         emit dataReq();
         break;
     case MSG_OPENED:
         emit open();
         break;
     case MSG_FINISHED:
         //qDebug() << "Finished [this = " << this << "]";
         d->offset = 0;
         d->speed_timer.stop();
         emit finished();
         break;
     case MSG_STAT_ENTRY: {
         UDSEntry entry;
         stream >> entry;
         emit statEntry(entry);
         break;
     }
     case MSG_LIST_ENTRIES: {
         UDSEntryList list;
         UDSEntry entry;
 
         while (!stream.atEnd()) {
             stream >> entry;
             list.append(entry);
         }
 
         emit listEntries(list);
         break;
     }
     case MSG_RESUME: { // From the put job
         d->offset = readFilesize_t(stream);
         emit canResume(d->offset);
         break;
     }
     case MSG_CANRESUME: // From the get job
         d->filesize = d->offset;
         emit canResume(0); // the arg doesn't matter
         break;
     case MSG_ERROR:
         stream >> i >> str1;
         //qDebug() << "error " << i << " " << str1;
         emit error(i, str1);
         break;
     case MSG_SLAVE_STATUS:
     case MSG_SLAVE_STATUS_V2: {
         qint64 pid;
         QByteArray protocol;
         stream >> pid >> protocol >> str1 >> b;
         emit slaveStatus(pid, protocol, str1, (b != 0));
         break;
     }
     case MSG_CONNECTED:
         emit connected();
         break;
     case MSG_WRITTEN: {
         KIO::filesize_t size = readFilesize_t(stream);
         emit written(size);
         break;
     }
     case INF_TOTAL_SIZE: {
         KIO::filesize_t size = readFilesize_t(stream);
-        d->start_time = QDateTime::currentMSecsSinceEpoch();
-        d->last_time = 0;
         d->filesize = d->offset;
-        d->sizes[0] = d->filesize - d->offset;
-        d->times[0] = 0;
-        d->nums = 1;
+        d->transfer_details.append({0, 0});
         d->speed_timer.start(1000);
+        d->elapsed_timer.start();
         d->slave_calcs_speed = false;
         emit totalSize(size);
         break;
     }
     case INF_PROCESSED_SIZE: {
         KIO::filesize_t size = readFilesize_t(stream);
         emit processedSize(size);
         d->filesize = size;
         break;
     }
     case INF_POSITION: {
         KIO::filesize_t pos = readFilesize_t(stream);
         emit position(pos);
         break;
     }
     case INF_SPEED:
         stream >> ul;
         d->slave_calcs_speed = true;
         d->speed_timer.stop();
         emit speed(ul);
         break;
     case INF_GETTING_FILE:
         break;
     case INF_ERROR_PAGE:
         emit errorPage();
         break;
     case INF_REDIRECTION: {
         QUrl url;
         stream >> url;
         emit redirection(url);
         break;
     }
     case INF_MIME_TYPE:
         stream >> str1;
         emit mimeType(str1);
         if (!d->connection->suspended()) {
             d->connection->sendnow(CMD_NONE, QByteArray());
         }
         break;
     case INF_WARNING:
         stream >> str1;
         emit warning(str1);
         break;
     case INF_MESSAGEBOX: {
         //qDebug() << "needs a msg box";
         QString text, caption, buttonYes, buttonNo, dontAskAgainName;
         int type;
         stream >> type >> text >> caption >> buttonYes >> buttonNo;
         if (stream.atEnd()) {
             messageBox(type, text, caption, buttonYes, buttonNo);
         } else {
             stream >> dontAskAgainName;
             messageBox(type, text, caption, buttonYes, buttonNo, dontAskAgainName);
         }
         break;
     }
     case INF_INFOMESSAGE: {
         QString msg;
         stream >> msg;
         emit infoMessage(msg);
         break;
     }
     case INF_META_DATA: {
         MetaData m;
         stream >> m;
         if (m.contains(QStringLiteral("ssl_in_use"))) {
             const QLatin1String ssl_("ssl_");
             const MetaData constM = m;
             for (MetaData::ConstIterator it = constM.lowerBound(ssl_); it != constM.constEnd(); ++it) {
                 if (it.key().startsWith(ssl_)) {
                     d->sslMetaData.insert(it.key(), it.value());
                 } else {
                     // we're past the ssl_* entries; remember that QMap is ordered.
                     break;
                 }
             }
         }
         emit metaData(m);
         break;
     }
     case MSG_NET_REQUEST: {
         QString host;
         QString slaveid;
         stream >> host >> slaveid;
         requestNetwork(host, slaveid);
         break;
     }
     case MSG_NET_DROP: {
         QString host;
         QString slaveid;
         stream >> host >> slaveid;
         dropNetwork(host, slaveid);
         break;
     }
     case MSG_NEED_SUBURL_DATA: {
         emit needSubUrlData();
         break;
     }
     case MSG_HOST_INFO_REQ: {
         QString hostName;
         stream >> hostName;
         HostInfo::lookupHost(hostName, this, SLOT(slotHostInfo(QHostInfo)));
         break;
     }
     case MSG_PRIVILEGE_EXEC:
         emit privilegeOperationRequested();
         break;
     default:
         qCWarning(KIO_CORE) << "Slave sends unknown command (" << _cmd << "), dropping slave";
         return false;
     }
     return true;
 }
 
 void SlaveInterface::setOffset(KIO::filesize_t o)
 {
     Q_D(SlaveInterface);
     d->offset = o;
 }
 
 KIO::filesize_t SlaveInterface::offset() const
 {
     const Q_D(SlaveInterface);
     return d->offset;
 }
 
 void SlaveInterface::requestNetwork(const QString &host, const QString &slaveid)
 {
     Q_D(SlaveInterface);
     Q_UNUSED(host);
     Q_UNUSED(slaveid);
     //qDebug() << "requestNetwork " << host << slaveid;
 
     // This is old stuff. We just always return true...
 
     QByteArray packedArgs;
     QDataStream stream(&packedArgs, QIODevice::WriteOnly);
     stream << true;
     d->connection->sendnow(INF_NETWORK_STATUS, packedArgs);
 }
 
 void SlaveInterface::dropNetwork(const QString &host, const QString &slaveid)
 {
     Q_UNUSED(host);
     Q_UNUSED(slaveid);
     //qDebug() << "dropNetwork " << host << slaveid;
 }
 
 void SlaveInterface::sendResumeAnswer(bool resume)
 {
     Q_D(SlaveInterface);
     //qDebug() << "ok for resuming:" << resume;
     d->connection->sendnow(resume ? CMD_RESUMEANSWER : CMD_NONE, QByteArray());
 }
 
 void SlaveInterface::sendMessageBoxAnswer(int result)
 {
     Q_D(SlaveInterface);
     if (!d->connection) {
         return;
     }
 
     if (d->connection->suspended()) {
         d->connection->resume();
     }
     QByteArray packedArgs;
     QDataStream stream(&packedArgs, QIODevice::WriteOnly);
     stream << result;
     d->connection->sendnow(CMD_MESSAGEBOXANSWER, packedArgs);
     // qDebug() << "message box answer" << result;
 }
 
 void SlaveInterface::messageBox(int type, const QString &text, const QString &_caption,
                                 const QString &buttonYes, const QString &buttonNo)
 {
     messageBox(type, text, _caption, buttonYes, buttonNo, QString());
 }
 
 void SlaveInterface::messageBox(int type, const QString &text, const QString &caption,
                                 const QString &buttonYes, const QString &buttonNo, const QString &dontAskAgainName)
 {
     Q_D(SlaveInterface);
     if (d->connection) {
         d->connection->suspend();
     }
 
     QHash<UserNotificationHandler::MessageBoxDataType, QVariant> data;
     data.insert(UserNotificationHandler::MSG_TEXT, text);
     data.insert(UserNotificationHandler::MSG_CAPTION, caption);
     data.insert(UserNotificationHandler::MSG_YES_BUTTON_TEXT, buttonYes);
     data.insert(UserNotificationHandler::MSG_NO_BUTTON_TEXT, buttonNo);
     data.insert(UserNotificationHandler::MSG_DONT_ASK_AGAIN, dontAskAgainName);
 
     // SMELL: the braindead way to support button icons
     // TODO: Fix this in KIO::SlaveBase.
     if (buttonYes == i18n("&Details")) {
         data.insert(UserNotificationHandler::MSG_YES_BUTTON_ICON, QLatin1String("help-about"));
     } else if (buttonYes == i18n("&Forever")) {
         data.insert(UserNotificationHandler::MSG_YES_BUTTON_ICON, QLatin1String("flag-green"));
     }
 
     if (buttonNo == i18n("Co&ntinue")) {
         data.insert(UserNotificationHandler::MSG_NO_BUTTON_ICON, QLatin1String("arrow-right"));
     } else if (buttonNo == i18n("&Current Session only")) {
         data.insert(UserNotificationHandler::MSG_NO_BUTTON_ICON, QLatin1String("chronometer"));
     }
 
     if (type == KIO::SlaveBase::SSLMessageBox) {
         data.insert(UserNotificationHandler::MSG_META_DATA, d->sslMetaData.toVariant());
     }
 
     globalUserNotificationHandler()->requestMessageBox(this, type, data);
 }
 
 void SlaveInterfacePrivate::slotHostInfo(const QHostInfo &info)
 {
     QByteArray data;
     QDataStream stream(&data, QIODevice::WriteOnly);
     stream <<  info.hostName() << info.addresses() << info.error() << info.errorString();
     connection->send(CMD_HOST_INFO, data);
 }
 
 #include "moc_slaveinterface.cpp"
diff --git a/src/core/slaveinterface_p.h b/src/core/slaveinterface_p.h
index a4cb5d3f..efb17d0f 100644
--- a/src/core/slaveinterface_p.h
+++ b/src/core/slaveinterface_p.h
@@ -1,68 +1,71 @@
 /* This file is part of the KDE libraries
    Copyright (C) 2000 David Faure <faure@kde.org>
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License version 2 as published by the Free Software Foundation.
 
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.
 
    You should have received a copy of the GNU Library General Public License
    along with this library; see the file COPYING.LIB.  If not, write to
    the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
    Boston, MA 02110-1301, USA.
 */
 
 #ifndef KIO_SLAVEINTERFACEPRIVATE_H
 #define KIO_SLAVEINTERFACEPRIVATE_H
 
 #ifdef Q_OS_WIN
 #include <qt_windows.h>
 #include <winsock2.h> // struct timeval
 #endif
 
 #include "global.h"
 #include "connection_p.h"
 #include <QTimer>
 #include <QPointer>
 #include <QHostInfo>
+#include <QVector>
+#include <QElapsedTimer>
 
 #include "kiocoredebug.h"
 
-static const unsigned int max_nums = 8;
+static const unsigned int max_count = 8;
 
 class KIO::SlaveInterfacePrivate
 {
 public:
     SlaveInterfacePrivate()
-        : connection(nullptr), filesize(0), offset(0), last_time(0), start_time(0),
-          nums(0), slave_calcs_speed(false)
+        : connection(nullptr), filesize(0), offset(0),
+          slave_calcs_speed(false)
     {
     }
     virtual ~SlaveInterfacePrivate()
     {
         delete connection;
     }
 
     Connection *connection;
     QTimer speed_timer;
 
     // We need some metadata here for our SSL code in messageBox() and for sslMetaData().
     MetaData sslMetaData;
 
-    KIO::filesize_t sizes[max_nums];
-    qint64 times[max_nums];
+    struct TransferInfo {
+        qint64 time;
+        KIO::filesize_t size;
+    };
+    QVector<TransferInfo> transfer_details;
+    QElapsedTimer elapsed_timer;
 
     KIO::filesize_t filesize, offset;
-    size_t last_time;
-    qint64 start_time;
-    uint nums;
     bool slave_calcs_speed;
 
     void slotHostInfo(const QHostInfo &info);
 };
 
 #endif